A computer assisted cardiogram diagnosis is to analyze the cardiogram signal automatically, and to provide commonly used parameters of clinical diagnosis as well as possible diagnostic conclusions for physicians' reference. The study of computer assisted cardiogram diagnosis started from 1960. At the beginning, it was confined to research in laboratories only. However, it has been incorporated into clinical practices gradually. Up to now, some of the programs are even available for commercial distributions. The method of computer assisted cardiogram diagnosis can be sorted into two approaches: the first is to construct parameters using purely engineering analytic method, for recognizing or predicting particular pathological signals, such as the complexity index for judging ventricular fibrillation, the hidden Markov matrix for judging atrial fibrillation, the heart-rate variance analysis index for calculating threat of a sudden death, and etc.; whereas, the second is to simulate the process of a clinical judgment done by a physician, by means of converting and quantifying his/her judging method, for achieving a corresponding diagnostic analyzing function. The first approach is generally used to discriminate for recognizing a minority of particular pathological signals, and it mainly remains in research at present. By comparison, the second approach has seen a wider usage, by which more types of pathological signal diagnoses can be achieved.
In the actual design of a computer assisted diagnostic system, the judging method applied in the system is unlikely to be made perfect in a single time of design. Usually, a prototype is designed in the first place, whereof the method is modified over and over again through a large number of clinical tests. If it was a regular logic judging structure adopted, each of the modifications will surely cause tremendous changes to the rules for the judgment. Currently, direct logical judgment in simulation of a physician's judgment process is commonly used to achieve those corresponding functions. However, when there are hundreds of types of pathology to be judged, the rules for the pathological judgment may conflict or overlap with each other, thereby making the logical structure of the program extremely complicated and the process of judgment vulnerable to mistakes. To solve the conflicts between those diagnostic rules, therefore, it requires that the logical structure of the direct judgment process be adjusted and modified, and if to adjust the logical structure, the existing system must be largely updated and modified, as a result of which the improvement and maintenance of the diagnostic systems will be rendered extremely difficult.
As an infrequent approach, expert inference system software is also used to provide the judgment by registering those relating rules into the system and depending on the kernel of the expert inference system for executing the judgment. For example, the ECG Criteria Language (ECL), as one of commercial expert inference systems, defines a co-understandable language between the physician and the computer. In that system, the diagnostic analysis is completed via the inferring kernel as the diagnostic rules of the physicians are registered into the system. However, since the approach cannot be separated from the deriving kernel, its applications in practice are strictly limited.